The systematic position of some Ethiopian Nippostrongylinae

Transcripción

Onderstepoort Journal of Veterinary Research, 72:55–65 (2005)
The systematic position of some Ethiopian
Nippostrongylinae (Nematoda, Trichostrongylina,
Heligmosomoidea) from the National Collection of
Animal Helminths, Onderstepoort, South Africa
M.-C. DURETTE-DESSET1 and M.-C. DIGIANI2
ABSTRACT
DURETTE-DESSET, M.-C. & DIGIANI, M.-C. 2005. The systematic position of some Ethiopian
Nippostrongylinae (Nematoda, Trichostrongylina, Heligmosomoidea) from the National Collection of
Animal Helminths, Onderstepoort, South Africa. Onderstepoort Journal of Veterinary Research, 72:
55–65
The taxonomic status of some nippostrongyline nematodes deposited in the National Collection of
Animal Helminths, Onderstepoort, is revised. Heligmonina boomkeri n. sp. is described from Aethomys chrysophilus from South Africa. The most closely related species by the body measurements
and the pattern of the caudal bursa is Heligmonina bignonensis Diouf, Bâ & Durette-Desset, 1997,
a parasite of Mastomys erythroleucus from Senegal. It differs from the new species mainly in the
number of ventral cuticular ridges at mid-body (four versus five) and the left ala in the male is shorter
than the body diameter. The systematic position of Heligmonina spira (Ortlepp, 1939) and Neoheligmonella capensis (Ortlepp, 1939) is confirmed here through their synlophe, which was not previously studied.
Keywords: Ethiopian region, Heligmonina boomkeri n. sp., Heligmonina spira, Murinae, Nematoda,
Neoheligmonella capensis, Nippostrongylinae, synlophe, Trichostrongylina
INTRODUCTION
The Nippostrongylinae (Heligmonellidae) are parasites of relatively recent appearance, during the
Upper Miocene (Durette-Desset 1985). They may
have spread throughout the world with the migrations of their hosts, the Muridae. The group lends
itself particularly well to molecular studies, the
hosts being easy to capture and not considered as
rare species in need of protection. A phylogeny of
the Trichostrongylina based on morphological features was proposed by Durette-Desset (1985).
However, a comparison of the phylogenies of the
Nippostrongylinae based on morphological and on
molecular characters, such as the ITS 1 and ITS 2,
has not been made. Before embarking upon this
work, it was necessary to clarify the systematic
position of some species in which the synlophe, the
main character used for the determination of a species, is not known or was insufficiently described.
This study concerns the species described by Ortlepp (1939) in South Africa.
MATERIAL AND METHODS
1
Département de Systématique et Evolution, Muséum national d’Histoire naturelle, UMR 7138 associée au CNRS, CP 52,
61 rue Buffon, 75251 Paris cedex 05, France
2
División Zoología Invertebrados, Facultad de Ciencias Naturales y Museo, Universidad Nacional de La Plata, Paseo del
Bosque s/n, 1900 La Plata, Argentina
Accepted for publication 28 September 2004—Editor
The specimens studied originated from the National
Collection of Animal Helminths (NCAH), formerly
known as the Onderstepoort Helminthological Collection. They are very fragile and, in some, the cuticle was damaged or separated from the body on
cross-section. The state of preservation of the speci55
Ethiopian Nippostrongylinae (Nematoda, Trichostrongylina, Heligmosomoidea) from Onderstepoort, South Africa
mens determined the accuracy of our descriptions,
as some features were hardly visible or were absent
due to attrition. The nomenclature used for taxa
above the family group is that of Durette-Desset
(1985) and that for the structures of the caudal
bursa is that of Durette-Desset & Chabaud (1981).
The cuticular ridges were numbered from left to
right for the dorsal and ventral sides, both being delimited by the lateral fields which were always visible. The curve of the left ala is not included in the
measurement of its length. Where necessary, this
length is compared with the diameter of the body at
the level of the lateral fields (Fig. 2A). All measurements are in micrometers except where otherwise
stated. The measurements of the female paratypes
of the new species are indicated in parentheses.
The material of the new species is deposited in the
NCAH, Onderstepoort, South Africa and the Helminthological Collection of the Muséum national
d’Histoire naturelle, Paris, France (MNHN). The
nomenclature of the hosts is that of Musser & Carleton (1993).
IDENTIFICATION OF THE SPECIES
Heligmonina boomkeri n. sp.
TYPE
MATERIAL
Holotype male, allotype female, nine male and two
female paratypes, access number MNHN 331 MQ
of nerve ring variable. Excretory pore situated within posterior quarter of oesophagus. Deirids at same
level of or posterior to excretory pore (Fig. 1).
Oesophagus about 10 % of body length. Left ala
longer than body diameter. Very short vestibule
slightly longer than sphincter. Ratio of uterus length
to body length less than 25 %.
SYNLOPHE
In both sexes the body bears continuous cuticular
ridges, appearing just posterior to cephalic vesicle,
except left dorsal ridge adjacent to lateral field (no. 1
in Fig. 1C) and disappearing 70 µm anterior to caudal bursa in male (Fig. 1D). In the female, ventral
ridges disappear at different levels between the
infundibulum and vulva (Fig. 1E–G and 2D–G), dorsal ridges and left ala disappear at about 40 µm
from anus (Fig. 1H). Number of ridges: in female, at
level of oesophago-intestinal junction, 13 (left hypertrophied ala, six dorsal, six ventral) (Fig. 2C); in
both sexes, at mid-body, 12 (left ala, six dorsal, five
ventral) (Fig. 2A and B). At mid-body, double gradient of size, decreasing from left to right on ventral
side and from right to left on dorsal side. In section,
left ala longer than body diameter in male, shorter
in female (Fig. 2A and B). At mid-body, absence of
ridges on right, ventral-right quarter. At mid-body,
axis of orientation directed from ventral right to dorsal left side and inclined at 70 ° on sagittal axis in
male, 65° in female (Fig. 2A and B).
HOLOTYPE
HOST
Aethomys chrysophilus (De Winston, 1904) Muridae, Murinae
SITE
Duodenum
GEOGRAPHIC
ORIGIN
Jonkershoek, Stellenbosch, South Africa
VOUCHER
MATERIAL
One female, MNHN 332 MQ, a parasite of Rhabdomys pumilio vittatus from Jonkershoek, Stellenbosch, South Africa, coparasite of Neoheligmonella
capensis (Ortlepp, 1939).
GENERAL
Very small nematodes, body curved along the ventral side, anterior end in one or two spirals. Position
56
MALE
Holotype male is 2.3 mm and 95 wide at mid-body,
left ala included; cephalic vesicle, 48 long and 27
wide; nerve ring, excretory pore and deirids situated at 120, 205 and 215 from apex, respectively;
oesophagus, 215 long (Fig. 1A).
Asymmetrical caudal bursa with left lateral lobe
more developed and pattern of type 1-3-1 (rays 2
and 6 separating the first from common trunk of
rays 2–6) in right lobe and 1–4 (ray 2 separating the
first from common trunk of rays 2–6) in left lobe with
tendency to type 1-3-1 (Fig. 2I and J). Left lobe: ray
6 arising the first from common trunk of rays 3–6,
then ray 3. Ray 4 the most developed, thicker and
slightly longer than ray 5. Rays 4 and 5 distally
divergent. Ray 6 short (Fig. 2I). Right lobe: ray 5
arising the first from common trunk of rays 3–5.
Rays 8 arising proximally on trunk of dorsal ray, left
ray longer than right one. Dorsal ray divided into
two branches at its proximal third, each branch giving rise to two small branches, rays 9 (external
branches) longer than rays 10 (internal branches).
M.-C. DURETTE-DESSET & M.-C. DIGIANI
FIG. 1
Heligmonina boomkeri n. sp. A, male, anterior part, left lateral view. B, C, male, origin of the cuticular ridges, right and left
lateral views. D–H, posterior part where the ridges disappear. D, male, right lateral view; E–H, female, E, left lateral view,
F, right lateral view, G, ventral view, H, dorsal view
The ridges are numbered from left to right from no. 1–n for the dorsal side, no. 1'–n' for the ventral side
Scales: 50 µm
57
FIG. 2
Heligmonina boomkeri n. sp. A–G, synlophe in transverse sections of a male (2.65 mm long) and a female (3.1 mm long).
A, male, at mid-body (900 µm from the apex); B–G, female, B, at mid-body (1.4 mm from the apex), C, at the oesophagointestinal junction, D, at the level of the distal infundibulum, E, at the level of the sphincter, F, at the level of the distal
vestibule, G, just posterior to the vulva. H, female, posterior part, right lateral view. I, male, left lobe of the caudal bursa,
ventral view. J, other male, caudal bursa, ventral view
The ridges are numbered from left to right from no. 1–6 for the dorsal side, no. 1'–6' for ventral side. The arrows indicate
the disappearance of the ridges. All the ridges are orientated as in Fig. 2B
Abbreviations: r, right side, v, ventral side, ab: body diameter
Scales: A–G: 25 µm; H–J: 50 µm
58
Filiform, alate spicules, 418 long with sharp tips (Fig.
2J). Ratio of spicules length/body length: 18.4 %.
Gubernaculum not distinct. In one specimen, a slight
thickening of the cuticule of the spicular canal may
represent this structure (Fig. 1D). Genital cone not
visible (see below).
MAIN
MEASUREMENTS (AVERAGE AND RANGE) OF
NINE PARATYPES
Paratypes are 2.6 (2.0–3.0) mm long, 123 (100–
150) wide at mid-body, left ala included; cephalic
vesicle, 52 (46–60) long and 25.5 (21–30) wide;
nerve ring (n = 8), excretory pore and deirids situated at 134 (120–160), 200 (180–240), 210 (180–
235) from apex, respectively; oesophagus 227
(200– 260) long; spicules 406 (370–430) long; ratio
spicules length/body length, 15.5 (15.1–17.6) %;
genital cone visible only in one paratype, 20 long
and 18 wide.
FEMALES (ALLOTYPE
AND PARATYPES)
Females are 3.9 (3.4, 3.1) mm long and 95 (100,
90) wide; cephalic vesicle, 40 (55, 50) long and 23
(20, 25) wide; nerve ring, excretory pore and deirids
situated at 140 (160, 130), 185 (220, --) and 223
(230, --) from apex, respectively; oesophagus, 235
(290, 230) long.
Monodelphic. Vulva situated at 165 (140, 150) from
caudal extremity. Vagina vera, 42 (50, 40) long. Ovejector 150 (145, 152) long with vestibule 50 (50, 55)
long, sphincter 30 (23, 25) long and 45 (40, 50)
wide, infundibulum 70 (72, 72) long. Uterus 550
(740, 700) long with 12 (14, 13) eggs, at morula
stage, 63 (60, 57) long and 40 (40, 35) wide on average, arranged in one row. Tail 40 (35, 40) long with
rounded extremity (Fig. 2H).
MAIN
MEASUREMENTS OF THE FEMALE PARASITE
FROM
RHABDOMYS
chrysophilus are close to the species described by
Ortlepp (strong asymmetry of the lateroventral
lobes of the caudal bursa, left ray 8 longer than the
right one, gubernaculum not distinct), they are differentiated by the length of the left ala which is
about half the body width and not two-thirds as in H.
stellenboschius. In addition, right rays 3 and 4 on
the one hand and left rays 4 and 5 on the other are
joined except at their distal extremity. The association of these two latter characters of the caudal bursa
is present only in Heligmonina bignonensis Diouf,
Bâ & Durette-Desset, 1997, a parasite of Mastomys
erythroleucus from Senegal which is the most closely related species by the body measurements and
the pattern of the caudal bursa. Heligmonina bignonensis is differentiated by the more anterior position
of the excretory pore, by the number of ventral cuticular ridges at mid-body (four versus five), by the left
ala in the male being shorter than the body diameter, and by the length of left ray 6 being almost
equal to that of ray 5 (approximately half the length
of ray 5 in the specimens described above). We
consider the specimens from Aethomys chrisophila
as belonging to a new species which we have named
Heligmonina boomkeri n. sp. in honour of our colleague, Prof. Joop Boomker.
Heligmonina spira (Ortlepp, 1939)
Durette-Desset, 1971
= Heligmospiroides spira Ortlepp, 1939; = Longistriata ortleppi Desset, 1964
STUDIED
MATERIAL
Two males, three females syntypes
HOST
Rhabdomys pumilio vittatus (Wagner, 1842) Muridae, Murinae
PUMILIO
Female parasite is 3.5 mm long and 75 wide at midbody; cephalic vesicle, 54 long and 21 wide; nerve
ring and excretory pore situated at 130 and 220
from apex, respectively; oesophagus 280 long; vulva
situated at 160 from caudal extremity; ovejector 140
long; uterus 710 long with 13 eggs, 60 long and 40
wide; tail 58 long.
SITE
Duodenum
GEOGRAPHIC
ORIGIN
GENERAL
REMARKS
The specimens mentioned above were registered
in the Onderstepoort collections as “Heligmonina
stellenboschius Ortlepp, 1939”, a parasite of Myomys verroxii. Although the specimens from A.
Small nematodes, tightly curved along their ventral
side, following four spires in male, four to five in
female. In posterior part of female, body curved
along dorsal side and vulva and anus open at external side of body. Excretory pore situated within pos59
FIG. 3
Heligmonina spira (Ortlepp, 1939). A, male, anterior part, ventral view. B, C, female, origin of the ridges, right and left lateral views. D, E, female, area where the ridges disappear, right and left lateral views
The ridges are numbered from left to right, no. 1–n for the dorsal side, no. 1’–n’ for the ventral side
Scales: A–C: 50 µm; D, E: 100 µm
60
terior third of oesophagus. Deirids at same level or
posterior to excretory pore (Fig. 3A). Oesophagus
less than 7 % of body length in male, 6 % in female.
In male and female, left ala shorter than body diameter. Vestibule twice as long as sphincter. Ratio of
uterus length/body length less than 20 %. Eggs in
two rows except in distal part of the uterus.
SYNLOPHE
In both sexes, the body bears continuous cuticular
ridges, appearing between the cephalic vesicle and
excretory pore (Fig. 3B and C), except ridges no. 6
and 10’ which appear posterior to it. Ridges disappear anterior to caudal bursa in male. In female,
ridge no. 8’ disappears at about 800 anterior to
vulva (Fig. 4C), ridges no. 1 and 7’ at about 300
anterior to vulva (Fig. 4D), other ridges at different
levels between infundibulum and sphincter (Fig. 3D
and E). The left hypertrophied ridge disappears at
about 250 from vulva (Fig. 3E). Number of ridges at
mid-body: 16 (left ala, six dorsal, nine ventral) in
male (Fig. 4A), 15 (left ala, six dorsal, eight ventral)
in female (Fig. 4B). Dorsal gradient of size, decreasing from left to right. At mid-body, on ventral side,
gradient gradually decreasing from ridge no. 2’–5’
in male, from no. 2’–4’ in female, then ridges of
equivalent size. Left ala almost as long as body
diameter in both sexes. Presence of ridges on right,
right-ventral quarter at mid-body (Fig. 4A–D). Axis
of orientation at mid-body directed from right ventral
to left dorsal side and inclined on sagittal axis at 60°
in both sexes (Fig. 4A and B).
MALES
Males are 4.3, 4.4 mm long and 70, 65 wide at midbody, left ala included; cephalic vesicle, 55, 50 long
and 27, 35 wide; nerve ring and excretory pore situated at 160, 150 and 265, -- from apex, respectively; deirids observed only in first male, situated at 270
(left deirid), 285 (right deirid) from apex; oesophagus, 290, 280 long (Fig. 3A).
Asymmetrical caudal bursa with left lateral lobe
more developed and pattern of type 1–4 (rays 2
separating the first from common trunk of rays 2–6)
(Fig. 4F). Very long rays 3. Rays 3 and 6 arising at
same level from common trunk of rays 3–6. Rays 4
and 5 joined in two thirds of their length (right lobe),
divergent only at their extremities (left lobe). Rays 8
arising asymmetrically on trunk of dorsal ray. Dorsal
ray divided into two branches at its distal quarter,
each branch giving rise to two small equal branches, rays 9 (external branches) and rays 10 (internal
branches) (Fig. 4F).
Spicules filiform, with sharp tips. It was not possible
to measure the spicules and gubernaculum accurately. Very small genital cone, 15 long and 10 wide
at base with papilla 0 and papillae 7 well developed
(Fig. 4G).
FEMALES
Females are 5.9, 5.7, 6.2 mm long and 135, 140,
150 wide at mid-body, left ala included; cephalic
vesicle, 60, 55, 50 long and 38, 35, 40 wide; nerve
ring, excretory pore and deirids situated at 140,
160, 130; 185, 220, -- and 223, 230, -- from apex,
respectively; oesophagus, 235, 290, 230 long.
Monodelphic. Vulva situated at 215, 210, 230 from
caudal extremity. Vagina vera, 60, 55, 60 long.
Ovejector 258, 210, 245 long with vestibule 80, 70,
70, sphincter 40, 30, 35 long and 45, 40, 45 wide,
infundibulum 138, 110, 140 long, twisted at proximal part (n = 2). Uterus 1100, 950, 950 long with
25, 22, 30 eggs at morula stage, 73 long by 43 wide
on average, arranged in two rows. Tail 35, 40, 40
long with rounded extremity (Fig. 4E).
REMARKS
The specimens described above are parasites of
Rhabdomys pumilio and were named Heligmospiroides spira by Ortlepp (1939). The characters of
the synlophe, not previously described in transversal sections, allows us to confirm that the species
belongs to the genus Heligmonina, as proposed by
Durette-Desset (1971). In comparing our findings
with the detailed description of Ortlepp, we found
some differences that we consider as minor, namely that the body and various organs are longer. It is
interesting to note that, among the species of the
genus, the female of H. spira is the only one in
which the anus and the vulva open on the external
side of the spire. According to the description of
Ortlepp (1939) the male is the only one to have a
very complex gubernaculum.
Neoheligmonella capensis (Ortlepp, 1939)
Durette-Desset, 1971
= Longistriata (L.) capensis Ortlepp, 1939
STUDIED
MATERIAL
Two males, two females syntypes, coparasites of
Heligmonina boomkeri n. sp.
HOST
Rhabdomys pumilio vittatus (Wagner, 1842) Muridae, Murinae
61
FIG. 4
Heligmonina spira (Ortlepp, 1939) A–D, synlophe in transverse sections of a male (4.3 mm long) and a female (5.9 mm
long). A, male, at mid-body (2.2 mm from the apex); B–D, female, B, at mid-body (2.8 mm from the apex), C, at 800 µm
anterior to the caudal extremity, D, at 500 µm anterior to the caudal extremity. E, female, posterior part, right lateral view.
F, male, caudal bursa, ventral view. G, male, genital cone, ventral view
The ridges are numbered from left to right, no. 1–6 for the dorsal side, no. 1’–10’ for the ventral side. The arrows indicate
the disappearance of the ridges. All the ridges are orientated as in Fig. 4A
Abbreviations: r, right side, v, ventral side
Scales: A–F: 50 µm; G: 10 µm
62
and deirids situated at 190, 240; 290, -- and 300, --,
from apex, respectively; oesophagus 410, 425 long.
SITE
Duodenum
GEOGRAPHIC
ORIGIN
GENERAL
Small nematodes, tightly curved along their ventral
side. Excretory pore situated within posterior third
of oesophagus. Deirids at same level than excretory pore (Fig. 5A). Oesophagus less than 10 % of
body length in male, 6 % in female. In male and
female, left ala twice as shorter as the body diameter. Vestibule twice longer than sphincter with constriction at middle. Ratio uterus length/ body length
less than 20 %. Eggs in two rows except in distal
part of uterus.
Asymmetrical caudal bursa with right lateral lobe
more developed and pattern of type 2-3 with tendency 2-2-1 (Fig. 5I). Right lobe: ray 4 curved dorsally at extremity, longer than ray 5, ray 6 arising
first from common trunk to rays 4–6. Left lobe: rays
4–6 arising at same level from common trunk. Rays
8 longer than dorsal ray and arising at its base.
Dorsal ray deeply divided into two branches at level
of arising of rays 8, each branch giving rise to two
small branches, rays 9 (external branches), longer
than rays 10 (internal branches).
Spicules filiform, 350 long (in first specimen) with
curved tips S-shaped. Gubernaculum 35 long and
30 wide (in second specimen). Genital cone not
observed.
FEMALES
SYNLOPHE
In both sexes, the body bears continuous cuticular
ridges, appearing just posterior to cephalic vesicle,
except dorsal ridge of carene (no. 1) which appears
at level of excretory pore. In male, ridges disappear
anterior to caudal bursa except ridge no. 4 which
disappears within posterior quarter of body (Fig.
5E). In female, dorsal ridges no. 4 and 5 merge at
about 400 anterior to vulva. All ridges disappear at
level of vulva. Carene with dorsal ridge poorly developed in both sexes, except at the end of the anterior third in male (Fig. 5). Ridge no. 5 (in front of right
lateral field) well developed. Number of ridges at
oesophageal region (Fig. 5B) and at mid-body (5D
and F): 12 (carene, four dorsal, six ventral) in both
sexes; in female, at level of infundibulum, 11
(carene, three dorsal, six ventral) (Fig. 5G); just
anterior to vulva: 6 (two dorsal, two left and two
right lateral) (Fig. 5H). At mid-body, double gradient
of size of the ridges. On ventral side, gradient gradually decreasing from left to right, from ridge no.
2’–5’ then ridges of equivalent size. On dorsal side,
except dorsal ridge of carene, gradient gradually
decreasing from right to left. In female, ridges no. 1
and 5 most developed. Axis of orientation directed
from right ventral to left dorsal side and inclined at
about 60° on sagittal axis in both sexes (Fig. 5D
and F).
MALES
Males are 5.2, 4.7 mm long and 110, 150 wide at
mid-body, left ala included; cephalic vesicle 55, 60
long and 30, 35 wide; nerve ring, excretory pore
Females are 8.9, 6.9 mm long and 120, 140 wide at
mid-body, left ala included; cephalic vesicle 60, 60
long and 32, 44 wide; nerve ring, excretory pore and
deirids situated at 220, --; 350, -- and 340, 345 from
apex, respectively; oesophagus 430, 420 long.
Monodelphic. Vulva situated at 110, 120 from caudal extremity. Vagina vera --, 28 long. Ovejector
(observed only in first specimen) 250 long with
vestibule 65, sphincter 20 long and 33 wide, infundibulum 125 long. Uterus 1.4, 1.3 mm long with 56,
37 eggs at morula stage, 90 long by 50 wide on
average, arranged in two rows except in distal part
of uterus. Tail 56, 37 long with sharp extremity (Fig.
5M).
REMARKS
The specimens described above, parasites of
Rhabdomys pumilio were named Longistriata (L.)
capensis by Ortlepp (1939). The characters of the
synlophe, not described in transversal sections up
to now, allow us to confirm that the species belongs
to the genus Neoheligmonella, as proposed by
Durette-Desset (1971).
Neoheligmonella capensis is distinguished from the
other species of the genus by the S-shaped extremity of the spicules. However, the syntypes described
here differ from the specimens described by Ortlepp
(1939) in two characters, viz. the female tail, which
is straight, and the dorsal ray, which is divided in
the proximal part rather than at the distal one. This
latter feature is usually diagnostic at specific level,
and it is possible that the specimens studied here
63
FIG. 5
Neoheligmonella capensis (Ortlepp, 1939) A, male, anterior part, right lateral view. B-H, synlophe in transverse sections of
a male (5.2 mm long) and a female (8.9 mm long). B–E, male, B, at the level of the oesophago-intestinal junction, C, at the
end of the anterior third of body, D, at mid-body (3.1 mm from the apex), E, at 1.3 mm anterior to the caudal bursa; F–H,
female, F, at mid-body (3.4 mm from the apex), G, at the level of the infundibulum, H, just anterior to the vulva. I, male,
caudal bursa, ventral view. J, K, dissected tips of the spicules, J, right spicule, ventral view, K, left spicule, ventral view. L,
spicules in situ, ventral view. M, female, posterior part, left lateral view
The ridges are numbered from left to right, no. 1–5 for the dorsal side, no. 1’–7’ for the ventral side.
The arrows indicate the disappearance of the ridges. All the ridges are orientated as in Fig. 5D
Abbreviations: r, right side, v, ventral side
Scales: A, I, M: 100 µm; B–H, J–L: 50 µm
64
represent a new species. Since all the remaining
characters are identical to those described for N.
capensis, including the S-shaped extremity of the
spicules, we prefer to assign the specimens, at least
temporarily, to N. capensis, until such time more
material becomes available.
DESSET, M.-C. 1964. Les systèmes d’arêtes cuticulaires chez
les Nématodes Héligmosomes. Etude de cinq espèces parasites de Rongeurs de La Maboké. Cahiers de La Maboké,
2:39–78.
In the genus Neoheligmonella, the caudal bursa is
sub-symmetrical except in N. capensis and N. acomysi Durette-Desset & Gibson, 1990 in which the
right lobe is clearly more developed than the left
one. This character distinguishes the genera Neoheligmonella and Heligmonina Baylis, 1928. In the
latter, the asymmetry is always present with a more
pronounced development of the left lobe.
DURETTE-DESSET, M.-C. 1971. Essai de classification des
Nématodes Héligmosomes. Corrélation avec la paléobiogéographie des hôtes. Mémoires du Muséum national d’Histoire naturelle, nouvelle série, série A, Zooogie, 49:1–126.
ACKNOWLEDGEMENTS
DURETTE-DESSET, M.-C. & GIBSON, D.I. 1990. Neoheligmonella acomysi n. sp. (Trichostrongyloidea, Nippostrongylinae), parasite d’Acomys dimidiatus (Muridae) de Somalie.
Sysematic Parasitology, 17:109–113.
We thank Prof. Joop Boomker for the loan of the
material from the National Collection of Animal Helminths, Onderstepoort, South Africa.
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